The FAA already allows the use of a driver's license for "sport" flyers; no medical certificate required.
Personally, I'm in favor of retaining the third class medical.
I've met quite a few individuals who couldn't pass the third class medical, but who would go on to fly if that didn't stand as an obstacle. This is to say, I've met many individuals who aren't medically qualified to fly, but who would do it anyway, given the chance.
I have never been in favor of the sport pilot certificate, or the medical requirements behind it.
Presently the FAA extends the duration of third class privileges to five years for individuals under 40 years of age, or for those of us a little more "advanced," two years duration.
Still a pretty good deal, considering my first class only lasts six months.